jacobs



E. H. JACOBS.

ELECTRIC SWITCH.

APPLICATION FILED MAR. 9. 1911.

Patented Aug. 8, 1916.

5 SHEETS-SHEET I.

Inventor Ernest H.Jacobs.

' Hi3 Attorney.

Ill nue w m. mAwJ a 5 a E. H. JACOBS.

ELECTRIC SWITCH.

APPLICATION FILED MAR.9.19H.

1,193,694. Patented Aug. 8,1916.

5 SHEETS-SHEET 3.

Witnesses: 37 Inventor mm; ,S u M Ernest H.Jacobs,

I His Attorney.

E. H. JACOBS.

ELECTRIC SWITCH.

APPLICATION FILED MAR. 9. 1911.

Patented Aug. 8, 1916.

5 SHEETS-SHEET 4.

wllllll I:

Inventor Ernest H-2J8C0b$ Witnesses:

\ is tforney.

E, H. JACOBS.

ELECTRIC SWITCH.

APPLICATION FILED MAR. 9. 1911.

m n M e m v m m m n 4 9 w 9 m m m Ernest H.Jacobs,

a za- His Attorney.

UNITED STATES PATENT OFFICE.

mnms'r H. .mcoias,v or SCHE'NECTADY, new YORK, assmnon 'ro GENERAL ELECTRIC COMPANY, A CORPORATION or NEW YORK.

ELECTRIC SWITCH.

To all whom it may concern:

Be it known that I, ERNEST H. Jnoons, a a citizen of the United States, residing at Schenectady, county of Schenectady, Stateclosed, the fixed contacts are electrically Y connected by a bridging contact controlled by operating mechanism which is generally mounted above onto one side of the switch and of which some parts project over the top of the switch between the leads of the circuit to be controlled. The operating mechanism and the parts thereof which extend between the leads are made of metal to secure the necessary strength and therefore the space between the leads of the circuit must be so great that those metallic portions of the operating mechanism which are between the leads, will not cause a breakdown from one lead to the other. Many of the parallel motion operating mechanisms for compelling the movable contact to move in a straight line are objectionable because certain parts of the mechanism are in be tween the leads or the fixed contacts, and the leads of the circuit must be spaced so far apart that the floor space occupied. by the switch is too great.

The object of my invention is to provide an improved switch which is particularly adapted for controlling circuits carrying large amounts of energy; in which the movable contact is given a straight line motion by means of a parallel motion operating mechanism mounted to one side of the switch I and having an actuating arm of minimum parallel motion mechanism are placed so far away from the live parts of the switch that'the mechanism does' n t ha e any tend- Specificatlon Letters Patent.

Patented Aug. 8, 1916.

Application filed March 9,1911. Serial No. 618,376.

ency to cause breakdown from one live part to another; in which the movable contact is positively guided in substantially a straight line so that it works easily and drops away from the fixed contacts quickly and cannot swing out of alinement withthe fixed con-' tacts; and in which the operating mechanism of the switch is thoroughly protected from the Weather and from 'in-jury,but may be'easily inspected when desired. 1

Another object of my invention is to provide an operating mechanism which will permit the switch to open independently of the position of the handle or other operating member in case conditions upon the circuit are abnormal when the switch is closed, and which will trip with greater ease and certainty thandevices of this kind heretofore used, particularly where the switch is large and the force transmitted through the opera'ting mechanism is great.

My invention will best be understood in connection with the accompanying drawings, which merely for purposes of illustration show some of the various forms in which my invention may be embodied and in which- Figure 1 is aview partly in section of a form of switch embodying my invention and particularly adapted for mounting upon a switch board or similar support; Fig. 2 is a detail view of the switch shown in Fig. 1; Fig. 3 is-a top and side view of a particular form of bridging contact which is useful in switches of the type shown in Fig. 1; Fig. 4 is a view partly in section of another form of switch embodying my invention and par ticularly adapted to control high potential circuits carrying great amounts of energy; Fig. 5 is a longitudinal section of the stationary contact and surrounding parts of the type of switch shown in Fig. 4; Figs. 6, 7, and 8 are detail views of the parallel motion operating mechanism of the switch. shown in Fig. 4, the mechanism being shown in different positions; Fig. 9 is a view in elevation of the switch shown in Fig. 4 with the handle and its connecting rods removed and the cover removed from the parallel motion mechanism so that the mechanism may easily be seen; Fig. 10 is a view of anotherform of my invention inwhich the movable contact is automatically released from the handle in case of overload or other abnormal conditions on the circuit, this figure showing the parts in the position-assumed by them when the switch is closed; Fig. 11 is a view of the same mechanism after it has been tripped automatically; and Fig. 12 is a view of the same mechanism in position ready to again close the switch.

The particular form of switch shown in Fig. 1 is especially adapted to be secured to a switchboard or other suitable support and to be operated by hand. As shown in the drawing, the switch has a horizontal frame 1 which may be secured to any suitable support and which carries the various parts of the operating mechanism and also acts as a cover for the switch. To the frame 1 is detachably secured an oil tank 2 containing a sufiicicnt amount of oil or other insulating liquid to submerge the contacts of the switch so that when the circuit is opened, the arc is extinguished by the oil. The switch shown is designed to control a three wire circuit and therefore six insulators 3, each provided with a flange 1 and secured to the f 'ame 1 by means of the clamp 5 are arranged in two parallel rows with three insulators in each row, corresponding to the leads in the circuit which is to be controlled. Through each insulator extends a metallic rod, not shown, which at its upper end is secured to a lead of the circuit and which on its lower end carries a fixed contact 6 in a position to be engaged by and to cooperate with a bridging contact 7. In the switch shown in the drawing for controlling three wire circuits there are three bridging contacts, each of which closes the circuit through one wire by making an electrical connection between a fixed contact on an insulator in one row and another fixed contact on the corresponding insulator in the other row. \Vhen the circuit is to be opened, the bridging contacts simultaneously drop away from the stationary contacts and the arcs which are formed as a result of opening the circuit are extinguished by the oil in the oil vessel 2. The extinction of the arcs is assisted by a jet of oil projected against the are, and in order to accomplish this result each bridging contact 7 is provided near the end with a funnel shaped recess 8 which flares out toward the bottom and is provided at the top with a slot 9, as best shown in Fig. 3, so that as the bridging contact 7 drops down the oil caught in the recesses 8 is projected through the slots 9 and tends to disrupt the arcs. On practically all three wire, and particularly on three wire three phase circuits, all of the bridging contacts 7 should move together and therefore in the particular form of switch shown each bridging contact is rigidly clamped or otherwise secured to the lower end of an insulating rod 10, usually made of wood or other suitable material, and preferably mounted to move vertically and to slide through the guide bushing 11 in the top of the switch, All of the rods 10 are connected at the upper end to a common yoke 12 which is mounted parallel to the two rows of insulators and midway between them, and is so constructed that its lateral dimensions are as small as possible in order to minimize danger of a breakdown from one lead to the other through the yoke.

- The yoke 12 and the bridging contacts secured to it must be moved up and down in a vertical plane in order that the circuit may be opened and closed, and in order to do this I provide some suitable form of operating mechanism of which every part between the leads of the circuit is at least as narrow as the yoke 12. In accordance with my invention, the yoke 12 is suspended from the outer end of an arm or operating lever which extends between the insulators and the leads,

-and which moves in the same plane as the yoke 12. This arm 13 is so proportioned that it is no wider than the yoke 12 so that the presence of the arm between the leads does not reduce the striking distance between leads. The other or inner end of the arm 13 is pivotally connected at one point to the links 14. each of which is connected at one end to the arm 13 and at the other end to a pivot 15 firmly fixed to the frame 1. The arm 13 is also pivoted at a point eccentric to the point where it is pivoted to the links 14, to similar links 16, which are pivoted at one end to the arm 13 and at the other end to a bell crank 17 mounted upon the pivot 15. The bell crank 17 is rocked about the pivot 15 by any suitable mechanism, not shown. The outer end of the arm 13 connected to the yoke 1:2 is compelled to move in a straight line by a guide link 18 pivoted at one end to the link 16 and mounted at the other end on a pivot 19 carried on the frame 1, this guide link being of such a length and so related to the link 16 that the whole linkwork forms a parallel motion mechanism which compels the outer end of the arm 13 to move in a straight line and permits the yoke 12 and the bridging contacts 7 to move up and down with a minimum friction and maximum speed. The straight line movement of the contacts practically eliminates friction of the rods 10 in the guide bushings 11. consequently the operation of the switch is easy and rapid. As the switch opens the operating mechanism moves from the position shown in Fig. 1 to the position shown in Fig. :2. All the parts of the parallel motion mechanism are pivoted to each other and the weight of the mechanism is carried by the pivot 15, consequently the frictional resistance offered by the parallel motion to the opening of the switch is very slight, and the bridging contacts 7 drop away from the stationary contacts 6 with great rapidity.

When the potential of the circuit to be controlled is high and the amount of energy flowing in the circuit is great, the form and dimensions of the switch must be modified, and in Fig. 4 I have shown a form of switch embodying my invention and well adapted to control such circuits. In this particular form of switch an oil tank 20 containing a suflicient amount of oil to submer e the contacts of the switch stands upon t e floor of the station and is provided with a cover 21, preferably consisting of two dome shaped portions separated by a comparatively narrow gap. In eachof said portions there is an insulator 22 having a central conducting rod with its upper end connected to a lead of the circuit to be controlled and its lower end secured to some suitable form of fixed contact. The circuit is controlled by means of a bridging contact 23 which moves into and out of engagement with the fixed contacts on the lower ends of the insulator 22 and which is carried by an insulating rod 24 with its upper end extending above the surface of the oil in the oil vessel 20. The rod 24 is moved up and down by an operating mechanism comprising an arm 25 which extends between the insulators 22 and which is connected at one end to the upper end of the rod 24, the other end being pivotally connected to one end of a link 26, of which the other end is mounted on a stationary pivot 27 fixed in some suitable support, such as a bracket 28 carried upon the cover 21. The pivot 27 carries an actuating lever 29 which has one end mounted on the pivot 27 and the other end connected to a second link 30, which in turn is connected by a pin 31 to the arm 25 at a point eccentric to the point at which the arm connects with the link 26. A guide link 32 pivoted at one end to the "link 30 and mounted at the other end on a stationary pivot 33 guides the mechanism and the arm 25 in such a way that the point on the arm which is connected to the upper end of the rod 24, moves in a straight line, so that the whole operating mechanism is a parallel motion mechanism. In the particular arrangement shown, the force for moving the operating mechanism is transmitted to the operating mechanism through a link 34 which is pivotally connected to the link 29' of the parallel motion mechanism and to a rocking member 35 mounted upon a fixed pivot 36 and rocked about that pivot by rods the upper end of the rod 24 as a center is 43 to the arm 25 and also linked by means of the link 44 to a fixed point or pivot 45 on the bracket 28. The links 43 and 44 areso proportioned that when the parallel motion mechanism is rocked about the pivot 27, both the outerend of the arm 25 and the pin 42 on the outer end of the control link 41, move in parallel straight lines and the rod is positively guided and compelled to move in the desired path.

The different positions assumed by the operating mechanism as the switch opens and closes are shown in Figs. 6, 7, and 8, which are enlarged views of the mechanism shown in Fig. 4. In Fig. 6 the operating mechanism is in the position assumed by it when the switch is open, at which time the rocking member 35 is stopped in the required position by a suitable stop 46 which is rigidly secured to the bracket 28. As the operating handle 39 is moved to close the switch the operating mechanism gradually assumes the position shown in Fig. 7, where the switch is about half closed, while by the time the switch is fully closed the actuating toggle formed by the member 35 and link 34 is nearly straight and the parts of the operating mechanism assume the position shown in Fig. 8, at which time the upward movement of the switch is stopped by means of leaf springs 47 which are engaged by the pin 31 and form a yielding cushion or stop for stopping the upward movement of the bridging contact.

One of the objects of my invention is to provide a switch which will not only control circuits of very high potential, but will also open the circuit when a large amount of energy is flowing. The construction which I prefer to use to accomplish this object is shown in longitudinal, section in Fig. 5,

which shows a portion of the lower end of one of the insulators 22 and the fixed contact carried by the insulator. As best shown in Fi 5, the insulator 22 is referably made up 0' a number of rings of insulating material set one on top of the other to form a tubular insulator. The rings are gripped between a cap 48 on, the upper end of the insulator and an insulating hood or shell 49 which is secured to the lower end of the 1nsulator and is preferably made of porcelain or similar material having considerable mechanical strength and high insulating value. A strong metallic chamber 50 is countersunk in and partially inclosed by the hood 49, and is connected with the cap 48 by a strong metal rod 51 which clamps the rings of the insulator 22 and the hood 49 between the chamber 50 and the cap 48. The metallic chamber 50 contains a stationary contact 52 which cotiperates with a conductor 53 mounted on the bridging contact 23. As the switch is operated the conducting rod 53 moves into and out of the metallic chamber 50 through a suitable vent which has walls of insulation and is the only outlet for oil put under pressure in the chamber 50. In the preferred construction the chamber is vented by a perforated insulating bushing 54 mounted in an insulating lining 55, which is supported by a metallic collar 56 threaded into the walls of the chamber 50. The outer walls of the chamber 50 are also protected by a covering of insulation 57 which extends over all of the outer surface of the chamber and is firmly held in position by being clamped between the chamber and the insulating collar or hood 49. On the lower end of the bushing 54 there is secured an insulating flange or nut 58 which is placed to leave a space between it and the outerinsulating' covering 57.

As a result of the construction above described, the stationary contact 52 is surrounded by and inclosed in a strong pressure retaining chamber filled with oil and having opposite the stationary contact 52 a vent through which the movable contact rod 53 must enter and leave the chamber 50 which is normally filled with oil. When the switch opens the arc is drawn in the vessel 50, the oil therein is put under high pressure by the action of the arc and the arc is quickly extinguished. If the arc'persists until it is drawn out of the chamber 50 through the vent in the bushing 54 it will be extinguished by the oil under pressure flowing out through the vent.

In order to prevent the arc from striking across from one fixed contact to the other and also from holdin over from the metallic walls of the exp osion chamber 50, to the movable contact rods 53 I increase as much as possible the resistance to puncture, of all insulating material between the arc and the walls of the metallic chamber 50. The greatest strain on the insulation is exerted on the walls of the bushing 54 as the arc is drawn through the bushing and. I therefore strengthen the insulation between the arc and the metal collar 56 by making the insulating bushing 54 somewhat smaller than the opening in the insulation 55. I also leave between the flange 58 on the insulating bushing and the insulating covering 57. a space, which communicates with the interior of the oil tank and the space between the bushing 54 and the linin 55, so that both these spaces are filled wit oil. As a result of this construction the arc cannot hold to the collar 56 and the walls of the explosion chamber, unless it breaks down the insulating bushing 54, then the film of oil between the bushing and the insulation 55, and then the insulation 55. This construction, in which a number of layers of material having different dielectric characteristics are superposed, offers a much greater resistance to breakdown than is offered by the same thickness of'the material of any one of the layers.

In some ca ses the switch actuating mechanism is mounted upon a support which is independent of the oil tank and contacts of the switch, but is fixed in some suitable relation thereto, so that the operating arm of the mechanism will project between the leads going to-the switch and will move between the leads and parallel to them for the purpose of operating the movable contact. In such cases the parallel motion mechanism for moving the operating arm should be as compact as possible so that the floor space occupied by the switch and its actuating mechanism shall be reduced to a minimum. In the preferred construction, illustrated in Figs. 10, 1.1 and 12, some suitable support 59 is provided on which the various parts of the parallel motion operating mechanism are mounted. In the particular form of mechanism shown, a switch actuating member suitably journaled or mounted on the support 59 and comprising a rock shaft 60 is provided with a rigid extension or arm 61 which forms part of the parallel motion mechanism. To the outer end of the arm 61 is pivoted a link 62 which forms part of the parallel motion mechanism and is pivoted at its outer end to an arm 63 to which the movable contact of the switch is, connected and by which the movable contact is actuated. One end of the arm 63 is pivotally connected to a link 64 mounted upon a suitable pivot 65 in the support 59. As the rock shaft 60 is moved the link 64 is swung on its pivot by means of a guiding toggle 66 which is connected through an actuating link 67 to the arm 61. The variousparts are so proportioned that as the actuating member 61 rocks about the rock shaft 60 as an axis, the arm 63 is moved up and down. to open and close the switch and owing to the action of the guiding tog le 66, the link 64 and arm 63 are so move that the end of the arm 63 and the movable contact conneoted to it move in a strai ht line.

During 'the opening 0 the switch the movable contact attains a comparatively high velocity and some sort of yielding or resilient stop should be provided to stop the downward movement of the movable contact without causing excessive strains or jars, and also to store up energy which will asist the operator to close the switch. A

spring 68 is connected at one-fend by a pin 50 held rigid,

69 to the link 62 and is connected at the other end by a pin 70 to the support 59, the parts being so proportioned that as the arm '63 moves downward to open the switch the spring 68 is put under strain and yieldingly stops the downward movement of the contact. The stretched spring also assists in closing the switch. The actuating member of the switch mechanism also comprises an arm 71 rigidly secured to the rock shaft 60 and an operating member 72, which is loosel mounted on the rock shaft andis mova 1e independently of the actuating mechanism by an operating handle controlled by the operator.

that, for instance, it is impossible for the operator to hold the switch closed on overload. In order to attain this result I provide between the operating member 72 and the arm 71 of the actuating member of the 25, switch mechanism some form of collapsible connection which normally forms a rigid and positive connection between the two members but which under definite and predetermined conditions will collapse and permit the members to move independently of each other. Various forms of collapsible connections may be used, but the preferred construction is that shown, which is particularly: adapted for use where the switch is large and the amount of force to be transmitted through the connection is great. In this preferred form of collapsible connection the operating member 72 is connected to the arm 71 through a normally underset 4o toggle consisting of a link 73 connected to the arm 71 through some suitable lost motion connection such as a pin 74 which enters a slot in the end of the link 73, so that the link can move to a certain extent independently of the arm 71, and of a second link 75 pivoted to the link 73 to form a normally underset toggle which always tends to collapse. In order that the underset main toggle 7375 may normally be ut at the same time will be in condition to collapse upon the occurrence of overload or other abnormal conditions on the circuit, some suitable device such as a sensitive form of locking toggle is provided for holding the main toggle extended.

50 mounted one link 78 of the locking toggle.

The other link 79 of the locking toggle has one end connected to the middle of the link 78 and the other end mounted on a pivot 80 secured to the operating member 72. The

. locking toggle 78-79 is also normally underset and is held against collapse by a latch 81 mounted on the pivot 80. The latch 81.

has nearone end a notch or other suitable means 82 for engaging the free end of the link 78 and near the other end a projection 83, which, when the switch is in the closed position, is inalinement with the core of an' electroresponsive device, such as an overload coil or solenoid 84. i

In order to facilitate straightening out the main toggle 737 5, the rock shaft is provided with an arm or projection 85 which is connected through a spring 86 to the operating member 72, this spring being so proportioned that it tends to straighten the main toggle 7 37 5.

Where the movable contact is arrested in ing mechanism be automatically controlled by the movement of the operating mechamsrn incident to the closing of the switch, so that the catch will be automatically moved to release the switch as soon as the operator begins to close the switch. In the preferred construction the switch is caught and held open by means of a latch 87 mounted on the support 59 in a position to actuate and engage the end of the arm 71 as the switch opens, this latch being provided with a lug or projection 88 so arranged that as the operator begins to close the switch b moving the operating member 72 the link 73 of the main toggle moves a short distance independently of the arm 71 and during this independent movement the end of the link engages the lug 88 and forces the latch 87 down, thereby releasing the arm 71 so that the switch is free and, can be closed.

When the switch is closed the parts are in the position shown in Fig. 10, where the main toggle 7375 is prevented from collapsing by the locking toggle 78-79, which in turnis held against collapse by the latch 81. If an overload or any other abnormal condition appears on the circuit the coil 84 is energized, the latch 81 is moved and releasesthe other end of the link 78 of the locking toggle, thereupon the locking toggle collapses and permits the main toggle to collapse so that the actuating member of the switch can move independently of the main operating member 72, and the parts then move to the position shown in Fig. 11 as the switch opens. In order to close the switch it is necessary that the operator move the operating member 72 in such a waythat the members 72 and 71 are again locked in rigid relation to each other, and this result is accomplished by moving the operating memher 72 to the position shown in Fig. 12, by which movement the main and locking toggles are straightened out and are held in the extended position by the latch 81 engaging the end of the link 78, whereupon the operating member and the actuating member are rigidly locked to each other and the switch can be closed by means of the operating member 72. If the overload is still on the circuit or if other abnormal conditions appear during the closing of the switch, the coil 84 is energized as the con-- tacts of the switch touch, whereupon the latch 81 is again actuated and the switch opens regardless of the position of the operatin handle and of the operating member $2.

Switches embodying my invention are often of considerable size and may under some circumstances b placed out of doors and to protect the contacts of the oil vesse 20 and the operating mechanism I provide some suitable cover 89, as shown in Fig. 9, which extends over the gap between the two dome shaped portions of the cover 21 of the switch and is so shaped that it fully protects the operating mechanism of the switch. Inspection and repair of the switch is rendered easy because of the fact that the cover 89 is detachably secured to the switch and may easily be removed to enable'the operator to, at will, remove the cover and look over the operating mechanism.

The various novel features of my invention are claimed in this application and in certain divisions of this application which I have filed.

My invention may be embodied in other forms than those shown and described and I therefore do not limit my invention to the precise arrangement disclosed, but aim in the appended claims to cover all modifications which are within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. In an electric switch, the combination of an oil vessel, a cover for said vessel having a projecting part which extends over one side of said vessel, relatively movable cooperating contacts mounted in said cover, an operating lever connected to one of said contacts, actuating mechanism mounted in and contained within said projecting part of said cover and connectec to said operating lever to cause the end thereof to move up and down to close and open the switch, and means extending out of said projecting part and connected to said mechanism to actuate said mechanism to open and to close said switch.

2. An electric switch comprising an oil vessel, a cover for said vessel having an extension which projects to one side of said vessel, means cooperating with said extensions to form a hood at one side of said vessel, stationary contacts mounted in said cover on opposite sides of sald hood, a movable bridging contact mounted to move vertically and to cooperate with said stationary contacts, an operating lever mounted in said hood to overhang said vessel with one end between said fixed con acts and connected to said movable contact, operating mechanism contained in said extension and connected to said operating lever to cause the end of said lever and said contact to move up and down, and means extending downward out of said hood and connected to said mechanism to actuate said operating lever to bring said movable contact into and out of engagement with said stationary contacts.

3. In an electric switch, the combination of an oil vessel, a cover for said oil vessel divided into sections, a stationary contact secured to one section, a second stationary contact secured to an adjacent section, each of said sections having a projection which extends beyond the side of said oil vessel, an operating lever mounted on said projections to overhang said oil vessel, a bridging contact suspended from the end of said operating lever to cooperate with said stationary contacts, and actuating mechanism mounted on said projections to one side of said vessel and connected to said operating lever to cause the end thereof to move up and down and to bring said movable contact into and out of engagement with said stationary contacts.

4. In an electric switch, the combination of an oil vessel, a cover for said oil vessel divided into sections, two of said sections being mounted adjacent each other to leave a space between them and having projections which extend beyond the side of said oil vessel, stationary contacts mounted on said sections of the cover, an operating lever pivotally mounted on said projections to move vertically between them and to overhang said oil vessel, a movable contact suspended from said operating lever, actuating mechanism mounted between said projections and connected to said operating lever to move said contact up and down, and a third section of said cover detachably secured to said other sections to form a hood which covers the space between said first mentioned sections and extends over said projections to protect said operating mechanism.

5. In an oil switch, the combination of an oil vessel, a cover for said vessel having an opening near the middle thereof, stationary contacts mounted on said cover on opposite sides of said opening, pressure retaining chambers surrounding said contacts and embedded in insulation and each having a vent in alinement with the stationary contact, operating mechanism rigidly mounted at one side of said tank and comprising an operating arm which overhangs said vessel in alinement with said opening, actuating mechanism connected to said operating arm, a movable contact suspended from said arm 5 and moved up and down by said actuating mechanism to pass through the vents in said pressure retaining chambers and cooperate with said stationary contacts, and a hood detachably secured to said cover to inclose said operating mechanism and to cover said open- In an electric switch, the combination of a fixed contact, a relatively movable cooperating contact mounted to move into and out of engagement with said fixed contact, a metallic pressure retaining chamber mounted on said fixed contact and having an opening in the wall opposite said contact, and an insulating lining for said opening comprising concentric layers of solid insulating materials which have different dielectric characteristics, said concentric layers being arranged with a space between them which is adapted to be filled with insulating fluid.

7. In an electric switch, the combination with relatively movable cooperating contacts, a metallic pressure retaining chamber mounted in one of said contacts and having in one wall an opening through which the other contact passes to engage the first contact, and an insulating lining for said opening comprising two concentric rings of solid insulating material spaced apart from each other and with the space between them communicating with the interior of said pressure chamber filled with an insulating fluid.

the case in the Patent Oflice.

[SEAL] o1. 175-2sa 8. In an electric switch, the combination with an oil vessel, of relatively movable contacts-mounted to separate in said vessel under oil, a metallic pressure retaining chamber surrounding one of said contacts and having opposite said contact an opening with insulating walls through which one'of said contively movable cooperating contacts mounted to separate beneath the oil in said vessel, a metallic pressure retaining chamber mounted on and surrounding one of said contacts and having in one wall an opening through which the other contact passes, a ring of insulation in said opening to protect the edges of said opening, an insulating bushing having a body portion smaller than the opening through said ring, said bushing having an inner flange in engagement with the inner edge of said ring and an outer flange spaced away from the outer edge of said ring to leave a passage through which oil may fill the space between the body of said bushing and said ring.

In witness whereof, I have hereunto set my hand this 7th day of March, 1911.

ERNEST H. JACOBS. Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

It is hereby certified that in Letters Patent No. 1,193,694, granted August 8, 1916, upon the application of Ernest H. Jacobs, of Schenectady, New York, for an improvement in Electric Switches) errors appear in the printed specification requiring correction as follows: Page ,1, line 2, strike out the article a page 6, liHes65-66, claim 2, for the word extensions read extension; page 7, line 28, 1 claim 7, for the word in read on; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of Signed and sealed this 19th day of September, A. D., 1916.

, F. w.. CLAY,

Acting Commissioner fPatente, 

